In various surgical procedures, fasteners in the form of staples or the like are employed for holding tissue portions together to facilitate healing of a wound or incision. For example, a locking staple, having a tongue and groove structure by which the staple is locked, is disclosed in U.S. Pat. No. 2,881,762. A metal staple especially adapted for ligating blood vessels is disclosed in U.S. Pat. No. 3,079,608. International patent application No. PCT/SU79/00049 discloses a variety of fastening devices and instruments for performing circular anastomoses on the large intestine. The aforementioned disclosures serve as examples of a wide variety of tissue fastening devices and techniques that may be employed in general and/or specific surgical situations.
One common type of fastening device for joining or holding together soft tissue portions is the generally "U"-shaped staple which is typically fabricated from a suitable metal. Such staples, although generally described as having two legs joined to define a "U"-shape when unclinched, may also be regarded as having a configuration of an "open" loop when unclinched. The legs need not necessarily be parallel but are typically adapted for penetrating the tissue portions and for receiving between them some of the tissue material.
Other examples of U-shaped or open loop staples, as well as of methods and instruments for applying such staples to tissue, are disclosed in U.S. Pat. Nos. 3,252,643, 3,482,428, 3,692,224, 3,790,057, 3,795,034, 3,889,683, 4,198,982, 4,316,468, and 4,319,576.
Other tissue fastening devices have been proposed and differ from staples per se in that these other devices may have a plurality of components and do not have to be clinched in the manner used to set a staple. One such device is disclosed in U.S. Pat. No. 4,060,089 and includes a fastener strip provided with a plurality of longitudinally spaced, parallel prongs which are adapted to penetrate two overlapped tissue portions from one side so that the distal ends of the prongs project from the other side of the tissue portions.
The fastener device further includes a retainer strip which is adapted to be placed on the other side of the tissue portions opposite the fastener strip to engage the ends of the projecting fastener strip prongs and thus secure the tissue portions tightly between the fastener strip and the retainer strip. The retainer strip defines frustoconical openings for receiving the fastener strip prongs which each include a plurality of spaced-apart, frustoconical engaging members for engaging the retainer strip at a desired position relative to the prongs. This provides for the capability of adjusting the distance between the fastener strip and the retainer strip. Such a fastening device may be fabricated from a biodegradable or absorbable material.
Yet another tissue fastening device having a plurality of components is disclosed in co-pending commonly assigned U.S. patent application Ser. No. 359,443 filed Mar. 18, 1982, abandoned. The fasteners disclosed in that application are made from various polymeric materials and the legs of the U-shaped staple portion of the fastener have a pointed taper to improve the penetration of the staple into tissue.
Although many of the above-discussed types of tissue fastening devices and techniques are satisfactory in various applications, there is a need to provide an improved fastening device, especially one completely fabricated from absorbable materials.
Also, it would be desirable to provide an improved fastening device fabricated from absorbable materials that can provide primary approximation of the tissue edges to insure that the tissue edges are in continuous contact. Further, such an improved fastener should provide a desired amount of hemostatic compression to minimize bleeding, but allow some collateral blood circulation to the wound or incision edges of the tissue to promote healing. In addition, such an improved fastener should have the capability to accommodate varying tissue thicknesses and should leave as little tissue cuff or margin as possible in effecting the joining of the tissue.
It is also desirable that the fastener cause as little trauma to tissue as possible. Hence when using a "U"-shaped fastener the legs of the "U" should be smooth, free of projection, so that the leg will readily penetrate tissue without tearing or causing undo trauma of the tissue.
Because humans are of different sizes and configurations and because tissue in the human body is of varying thickness it is desirable that polymeric fasteners be locked or set in place at any desired thickness and not at some predetermined thickness.
Further, it would be beneficial if such an improved fastener had a configuration that would enable the fastener to be fabricated with as small a size as possible to minimize the amount of implantable material. Also, another desirable feature of such an improved fastener would be a fastener configuration that minimizes the possible sites of formation of pockets of infection in the tissue.
Further, such an improved fastener would desirably provide the surgeon with tactile feedback and compensating control during the application of the fastener.
Finally, such an improved fastener should have the capability for maintaining the tissue portions in approximation and compression for a minimum of 21 days in vivo.
It would also be advantageous to provide such a fastener with a design that would facilitate its application to the tissue portions with a simple yet effective method. It would also be desirable if the improved fastener could readily accommodate application by means of an appropriately designed instrument.